Encryption has been used to provide for secure communication between participants in a radio communication system. One prior art arrangement is based on the use of a public algorithm, such as the Data Encryption Standard (DES), in conjunction with a privately maintained encryption key to enable secure communications. In such cases, it is common to periodically change the encryption keys to maintain the integrity of the system.
A radio communication system may employ multiple encryption keys, each governing communications for a particular subset of users on the system. In this manner, distinct communication groups may be created to provide for separate operation, or to provide for differing levels of security. It is known to provide a radio communication device with a set of encryption keys which are user selectable. In one approach, the user determines when a new key selection is required and enter the required key into the device. Another approach uses over-the-air rekeying transmissions or similar remote keying operation. Over-the-air rekeying allows systems to remotely reconfigure a radio communication device with a new key. One disadvantage is that once a key has been compromised the rekeying information is also available to an unauthorized listener. Another disadvantage is that the communication device needs to be available when rekeying is occurring throughout the system to retain secure communication capability.
It is desirable to provide for flexibility in the use of encryption keys when engaged in secure communications. The prior art implements a variety of methodologies of varying degrees of complexity and effectiveness. However, improvements are needed in the management of key selections for secure communications.